In connection with roller bearings used in high speed installations, such as in jet aircraft engines, roller wear has been a problem. Typically the ends of the rollers will wear, sometimes to the extent that the roller ends will become axle-like. As a result of this type of wear, the rollers are no longer properly guided by the races and a rocking motion can ensue due to gyroscopic forces. This motion will wear and eventually destroy the cage which will result in failure of the bearing. Wear problems have been accentuated as the bearing DN factor, the measure of linear surface speed as determined by the diameter of the bore of the rotating inner race in mm times the rotational speed in rpm, increases. For earlier jet aircraft engines, the DN was about 1.4 million but current engines have DN levels up to 2.4 million and it is anticipated that reliable bearing operation must be provided for advanced engines at a DN of 3 million and greater.
I have found that a two-row, low L/D (length/diameter) ratio bearing roller concept provides a bearing with no loss in radial stiffness compared to a conventional roller bearing and permits the use of a gyroscopically stable roller feature necessary for dependable high speed operation.
Wetherbee U.S. Pat. No. 3,980,359 shows a ball bearing construction in which a single row of balls is retained by a scalloped ring and in which the inner race is split. Keller U.S. Pat. No. 1,572,725 shows a plurality of tire-shaped rollers having slightly hollowed ends, and Derner et al. U.S. Pat. No. 3,713,712 discloses a roller bearing having hollow ends of almost circular concavity. The patent to Weibull, U.S. Pat. No. 1,622,985 teaches that for a desired shape of an "ellipsoid of inertia", the breadth of a solid cylindrical roller in a bearing must not exceed the product of the radius of the roller times .sqroot.3. Canadian Pat. No. 553,811 shows a bearing construction utilizing a pair of spherical rollers in separate concave inner raceways, the ends of the rollers being recessed to reduce stress concentration.